Bushing assembly



' Oct; .22, 1963 D. c. PALM 3,107,953

BUSHING ASSEMBLY Original Filed April 24, 1957 2 Sheets-Sheet 1 55 FIG.4

Oct. 22, 1963 D. c. PALM Original Filed April 24, 1957 2 Sheets-Sheet 2BUSHING ASSEMBLY United States Patent 3,1i97,953 BUSHENG ASSEMBLY Donald(1. Palm, Cuyahoga Falls, Ohio, assignor to The B. F. Goodrich Company,New York, N.Y., a corporation of New York Original application Apr. 24,1957, Ser. No. 654,948. Divided and this application May 29, 1961, Ser.No. 113,497

2 Claims. (Cl. 3tl836.1)

This invention relates to pivotal joints and more particularly to animproved resilient pivotal bushing assembly for use as a resilientconnector between pivotal links and the like. This application is adivision of my copending application Serial No. 654,948, filed April 24,1957, now abandoned.

The bushing assembly of this invention provides for substantiallyunimpeded pivotal movement of the parts it interconnects throughout awide oscillating range to gether with resilient cushioning of shockforces trans mitted to the bushing. In view of these characteristicsthese bushings are especially useful in automotive wheel suspensionmechanisms for connecting links of the suspension mechanisms to thevehicle frame. One particular advantage of these bushings for thispurpose is that they do not impose a so-called parasitic drag on thespring ing action of the main suspension springs, which is anobjectionable feature of the rubber torsion-type bushing assemblieswhich have been heretofore used for this purpose.

A resilient pivotal bushing assembly according to this invention ingeneral includes a pair of concentric bushing members having opposingbearing surfaces extending axially of the bushing members upon whichsurfaces the bushing members are rotatable relative to each other. Alsothere are transverse bearing surfaces at one end of the members adaptedfor mutual rotary engagement. lhe axial bearing surface of the least oneof the bushing members is defined by the series of resilient rubber ribsspaced apart axially of the assembly and which are rotatably engagedwith the bearing surface of the opposing bushing member. At least one ofthe transverse bearing surfaces is formed on a resilient rubber part.Means is provided adjacent at least one end of the assembly forresiliently interconnecting the bushing members for relative rotaryengagement to prevent axial displacement of the members and to seal thebearing surfaces from penetration of foreign matter. A lubricatingmaterial may be compounded directly into the rubber ribs, or a suitablelubricant separate from the rubber may be packed between the ribs. Inthe latter case the interconnecting means also functions to retain thelubricant between the bushing members.

In certain embodiments of the invention hereinafter de scribed, axialbearing surfaces of the bushing members are in the form of interrneshinghelical ribs generally resembling screw threads, at least one of thethreaded bearing surfaces being of resilient rubber. In theseembodiments the assembly is installed with its bus-hing members threadedtogether to a neutral position midway between the limits of apredetermined range of rotary oscillation. When the bushing members areoscillated by pivotal movement of the parts with which the assembly isassociated, the bushing members are threaded through one another Toountil their respective ribs are bottomed at the range limits, andmovement of the bushing members beyond the range limits tends to distortthe rubber portions of the bearing surfaces. Thus these threadedembodiments provide for substantially unimpeded rotary movement throughthe desired oscillation range but provide a marked snub bing action tooppose movement of the bushing members beyond the desired oscillationrange. These threaded embodiments are therefore especially suitable foruse in automobile suspension linkages.

The term rubber in this specification means both natural rubber andsynthesized materials having the elas ticity and resiliencecharacteristic of natural rubber.

Different forms of bushing assemblies embodying this invention are shownin the accompanying drawings to which reference will be made in thefurther explanation of the invention.

In the drawings:

FIG. 1 is a longitudinal cross-sectional view of bushing assembly madein accordance with the invention;

FIG. 2 is a plan view of a lower control arm of a typical automobilewheel suspension link in which bushing assemblies of FIG. 1 areoperatively installed;

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 2; and

FIGS. 4-9 show alternate forms of bushing assemblies embodying theinvention and suitable for use in an installation such as that of FIG. 2in lieu of the bushing assembly there shown.

Referring to FIG. 1, the bushing assembly there shown includes an outerbushing member 10 concentrically surrounding an inner bushing member 11.The outer member 10 is formed witha metal cylindrical sleeve 13 having acircumferentially continuous annular body of resilient rubber 14 bondedto the inner surface of the sleeve 13 and formed with a cylindricalinternal bearing surface 15.

The inner bushing member 11 includes a rigid tubular metal sleeve 18having adhered to its external surface an annular c-ircumferentiallycontinuous layer of resilient rubber 19. The rubber layer 19 is shapedto provide a series of annular circumferential ribs 20 spaced apart fromeach other axially of the assembly. Each of the ribs terminates in agenerally cylindrical outer surface 21 and these surfaces collectivelydefine the bearing surface for the inner bushing member 11. The ribs 29are of uniform height and axial width and are proportioned so that thetotal area of their outer surfaces 21 is equal to about of the opposingcylindrical surface 15 of the outer bushing member In before the partsare assembled. Generally the ribs will be compressed slightly after theassembly is made. After assembly of the inner and outer bushing membersthe internal bearing surface 15 of member 10 which is initially madecylindricaLis compressed slightly so that it bulges somewhat into thespaces be tween ribs 20* as shown in FIG. 1. In the operation of thisbushing the bearing surfaces 21 of the ribs 20 are adapted to rubagainst the opposing rubber bearing surface 15 when either of thebushing members is rotated relative to the other about their concentricaxis. Radial loads whether'sustained or intermittent are cushionedprimarily by radial'bulging of the resilient rubber ribs 2t). Inasmuchas the opposing bearing surfaoes'are of rubber for the bushing may beobtained.

Depending on the maximum radial loads imposed on the bushing assembly,the total area of the bearing surface of the ribs (the outer surfaces 21in FIG. 1) may range from about 30% of the opposing cylindrical bearingsurface up to about 75% of the opposing bearing surface. That is to say,the ribs may be made appreciably narrower where comparatively smallradial loads are imposed on the assembly.

Lubrication of the bearing surfaces may be obtained by compounding therubber parts with suitable lubricating ingredients incorporated therein.Preferably, however, the bushing members are assembled with the spacesbetween the ribs packed with a separate lubricant such as a grease (notindicated in drawing) which does not have deleterious effects on therubber parts. One lubricant suitable for this purpose is a commerciallyavailable silicon grease which is insoluble in water and which is stableover a temperature range of about '40 -F. to +400 F. Normally thebushing assemblies are packed with such grease when the bushing membersare assembled by their manufacturer and need not be repacked for thelife of the bushing. In automotive service, the bushing assembliesshould remain lubricated for the normally expected life of the vehicle.However, conventional grease fittings (not shown) could be utilized torepack these bushings periodically.

The bushing members 10 and 11 are rotatably interlocked when assembledas shown in FIG. 1 by means of an annular rubber ri'b formed on therubber layer 14 of member 10 and which projects radially intointerlocking engagement with a circumferential groove 26 in the rubberlayer 19 of inner bushing member 11. The end of the rubber layer 19 isappropriately tapered as at numeral 27 to facilitate this assembly. Whenthe outer and inner bushing members are forced axially together, the rib25 rides up the tapering end 19 and snaps into its groove 26 and isthereafter rotatable in groove 26 during relative pivotal movement ofthe bushing members but precludes relative axial displacement of thebushing members. The sealing rib 25 further prevents leakage of theluubricant from the bushing assembly and also keeps water, dirt andother foreign matter from entering between the hearing surfaces. Thebushing members are fitted together into an assembly as shown in FIG. 1with or without lubricant between their respective bearing surfaces asthe case may be, and the user in turn incorporates the assembly into aparticular linkage desired.

The bushing of FIG. 1 is particularly designed for automotive suspensionlinkages and, therefore, certain portions of the rubber layers 14 and 19are arranged to cushion axial forces imposed on the assembly. For thispurpose the rubber body 14 further includes an end portion 28' whichextends axially beyond the metal sleeve 13 and is adhered to a radiallyoutward extending flange 29 at the end of sleeve -13. The end portion 28includes an axial bearing face 30 adapted to embrace an opposing axialbearing face 31 formed on an end portion 32 of the rubber layer 19 ofthe inner member 11 when the bushing is assembled in a suspensionlinkage. The end portion 32 is seated wholly within the end portion 28of the outer bushing member 10. As. hereinafter explained,

' the bushing assembly is installed in a manner such that the rubber endportion 28 is axially compressed against flange 29 and squeezed aboutend portion 32 of the inner layer. Notwithstanding such axialcompression, however, the bushing members remain relatively rotatablewith substantially unimpeded pivotal movement.

In the bushing assembly of FIGS. 1-3 there is no re striction on therange through which the bushing members may be rotationally oscillatedrelative to each other. Normally, in these bushings the torque requiredto initially rotate one bushing member relative to the other (theso-called break-away torque) is greater than the torque required tosustain the rotary motion. However, even the break-away torque requiredfor this assembly is very much lower than the initial torque required todeflect rubber torsion bushings of equivalent size heretofore used forthis purpose. Moreover, by virtue of the ribbed configuration :of one ofthe bearing surfaces this bushing assembly provides materially softercushioning for radial bearing loads.

FIGS. 2 and 3 illustrate the manner in which bushing assemblies of thetype shown in FIG. 1 may 'be installed as the pivotal connectors of thelower control arm 35 of a typical automotive Wheel suspension linkage.The control arm 35 at its wide end includes two axial aligned annularbosses 36 through which project the opposite ends 37 of a pivot pin 38adapted to be secured to the frame (not shown) of a vehicle by lugs 39.A bushing assembly as in FIG. 1 is positioned in each boss 36 about theend 37 of pin 38 as shown in detail in FIG. 3. The bushing assembly isinstalled preferably with its outer metal sleeve 13 pressed into boss 36and with its inner metal sleeve 18 iastened to end 37 by a cap screw 42,a washer 43 and an annular end plate 44. The inwardly directed end ofthe inner sleeve 18 is plane and abuts a shoulder 45 of pin 38.- Toprevent inner sleeve 18 from rotating on 37 of pin 38, the outboard endof sleeve 18 is formed with serrations 47 (FIG. 1) which are engaged byintermeshing radial serrations (not shown) at 'the periphery of washer43. Alternatively, the inner bushing member may be secured on end 37 byany of various available fastening devices and the serrated constructionmay be omitted. The end plated-4- is dish-shaped and slightly compressesthe end portion 28 of the outer rubber portion 14 of the outer bushingmember 10 as indicated in FIG. 3. In the operation of this assembly, thecontrol arm 35 will be swung pivotally' relative to pin 38 to rotate theouter bushing members 10 freely about their respective inner bushingmembers 11. Axial forces on the bushing are cushioned by the radialoverlapping engagement of plate 44 with the rubber end portion 28, theouter radial face 28a of rubber portion 28 serving as a transversebearing surface for bushing member 10 and the inner face 44a of plate 44serving as a The bushing assembly 50 shown in FIG. 4 differs from theassembly of FIG. 1 primarily in that in the assembly 50, an outerbushing member 52, is formed wholly, of metal and has a smooth internalcylindrical bearing surface 53 which bears against an opposing bearingsurface 54 formed of resilient rubber ribs secured to the externalagainst the radial flange 57 by a plate 44. Near the opposite or inboardend of the outer member, there is an annular flange 62 which isresiliently interlocked with an annular groove 63 in the rubber body ofthe inner member. I

The bushing assembly 65 of FIG. 5 is the same con struction as that ofFIG. 4 except that in FIG. 5 the interior cylindrical bearing surface ofthe metal outer busha ing member 68 is covered with a thin coating 69 ofa polymer of tetrafluoroethylene, a material more commonly known asTeflon.

The bushing assembly 70 shown in FIGS. 6 and 7 in cludes an outerbushing member 71 formed of a cylindrical metal sleeve 72 having anannular body of rubber 73 secured to its internal surface. The innerbushing member 74 similarly is formed with an inner metal sleeve 75having a circtnnferentially continuous rubber body 76 secured to itsexternal surface. Theru'bber bodies 73 and 76 include a series ofannular ribs 73a and 76a, respectively, intermeshed with each other inthe manner shown. Preferably the outer bushing member 71 islontransverse bearing surface for the inner bushing member the othermember.

gitudinally divided into a pair of mating semicylindrical sections (seeFIG. 7) to facilitate the assembly of the parts. Spaces are providedbetween the outermost surfaces of the initermeshing ribs and theadjoining surfaces of the opposing bushing member to receive a supply oflubricant between the members. At the opposite ends of the inner bushingmember 74, there are radial flanges 78 which embrace the end most ribsof outer member 71 to provide a resilient interconnection between theinner and outer member opposing relative axial displacement of themembers. The bushing members are relatively rotatable with theirrespective ribs intermeshing. The ribs in this embodiment furtherprovide substantial axial stability for the bushing. Installation ofthis assembly 7 may be like that shown in FIG. 3, except that end plate44 may be omitted.

All the foregoing bushing assemblies are so designed that there is norestriction on the range of oscillation through which the bushingmembers may be rotated relative to each other. On the other hand, thebushing assemblies of FIGS. 8 and 9 described in the following remarksare designed for substantially unimpeded rotary oscillation through adefinite range and provide for opposing rotary displacement of thebushing members beyond the desired range.

In the bushing assembly 80* of FIG. 8, the tWo bushing members includeconcentric metal sleeves 81 and 82 to Which is secured, respectively,circumferentially con tinuous rubber bodies 83 and 84. The opposinghearing surface of the bodies 83 and 84 are in the form of intermeshinghelical ribs 83a and 84a, the bushing members being threaded togetherwith their ribs interengaged so that rotation of one bushing memberrelative to the other tends to advance the rotated member axially alongThe rubber body 83 of the outer bushing member includes an annularradially inwardly directed rib 86 at the right end of the assembly as itis viewed in FIG. 8 which rib 86 extends into an annular groove 87 inrubber body 84 of the inner member so that the rib is rotatable in thisgroove during relative rotary oscillation of the bushing members. Thewidth of groove 87 is substantially wider than rib 86, the width of thegroove being proportional to the desired oscillation range. Thus therelative axial travel of the bushing members is substantially arrestedwhen the members are displaced to a position where the rib 86 engageseither side of groove 87. The rib 86 also functions to retain grease orother suitable lubricant between the bushing members.

At the left end of the assembly as shown in FIG. 8, the outer rubberbody 83 includes a radially outward extending annular radial end portion89* secured to a radial end flange 90 of the outer sleeve 81. Radiallyoverlapping portion 89 is an annular radial end portion 92 of the innerrubber body 84. In the neutral position of the bushing members, theportions 89 and 92 are normally axially-spaced from each other as shownin FIG. 8 and the rib 86 is at about the axial center of groove 87. Whenthe outer bushing member is rotated in a direction to advance itrightward as in FIG. 8 the radial body portion 89 is eventually radiallyengaged with the radial body portion 92., and the resulting axialcompression of these members offers appreciable snubbing action onforces tending to rotate the bushing members an additional amount. Thebushing assembly is designed so that the rib 86 will be brought intoengagement with the left side of groove 87 at about the same time theradial end portions 89 and 92 are engaged so that the rib 86 offersadded resistance to further rotary movement of the bushing members.

On the inward radial face 94 of radial end portion 92 there is anannular lip 95 which fits into a correspondingly shaped groove 96 in theradial end face of end portion 89 to key these end portions togetherwhen 6 they are under compression and to prevent grease from beingsqueezed between these end portions.

Bushing assembly may be incorporated into a suspension control arm likethat shown in FIG. 2 in the same manner that the bushing of FIG. 1 isinstalled therein. In such an assembly it will be evident that end cap44 will embrace the end portion 92 of the inner rubber body to providesolid support for this body when the end portion 89 of the outer bushingmember is urged against it. In using the threaded bushing assemblies inan installation like FIGS. 2-3, preferably the direction of the helix ofthe ribs is of the same hand in both bushings. Thus depending on thedirection of the helix, the radial end portions of one bushing willprovide a snubbing action for upward pivotal movement of the control armrelative to the frame, Whereas the radial end portions of the otherbushing will become engaged to snub downward pivotal movement of thecontrol arm relative to the frame. 'Ilhe radial end portions of bothbushings will cooperate to cushion twisting loads imposed axially on thebushings.

The bushing assembly 97 shown in FIG. 9 is of generally similarconstruction as that shown in FIG. 8 except that in FIG. 9 the outerbushing member is formed of metal and includes on its interior bearingsurface a helical rib 97a which is engageable with a helical rubber rib98 formed on a rubber layer 99 secured to the inner bushing member. Thehelical rib 97a may be coated with a Teflon coating as explained inconnection with FIG. 5.

Depending on the service for which these bushings are used, the rigidshell portions thereof can be made of any rigid material such as moldednylon, hard rubber, etc. in lieu of metal. In all cases, however, atleast one of the bearing surfaces is formed of narrow resilient rubberribs spaced apart from each other axially of the bushing. Rubbercompounds having a hardness of about 70 Shore A durometer and adurability comparable to tire tread rubber stock is generallysatisfactory for the resilient rubber portions of the bushing members.

Variations in the constructions disclosed may be made Within the scopeof the appended claims.

What is claimed is:

1. A resilient pivlo-tal bushing assembly comprising a pair of bushingmembers arranged one concentric about the other, said members havingopposed bearing surfaces extending axially of the bushing assembly uponwhich surfaces said bushing members are rotatable relative to each otherin said concentric arrangement, the bearing surfaces of each of saidmembers being in the form of a rib disposed helically along therespective bushing members, the helical rib of one bushing memberintermeshing with the helical rib of the other bushing member, at leastone of said nibs being of resilient rubber, an annular resilient rubberbody on one end of one bushing member, a bearing surface formed on saidrubber body and disposed generally transversely of the bushing assemblyand rotatably engaged with a mating transverse bearing surface on saidother bushing member, said transverse bearing surfaces being pressedagainst each other in rotary engagement in response to axial thrustloads on the bushing assembly, and sealing means at the end of saidbushing assembly opposite said transverse bearing surfaces, said sealingmeans including an annular rib on one bushing member and an annularchannel in the other bushing member wider than said rib into which saidcrib projects whereby said bushing members are adapted for limitedunrestricted relative rotation in reverse directions from a neutralcentral as sembled position of said interme-shed helical ribs.

2. A bushing assembly as defined in claim 1 wherein the ribs of bothbushing members are of a resilient rubber material, and wherein saidtransverse bearing sur- References Cited in the file of this patentUNITED STATES PATENTS Smith Aug. 20, 1878 Sherwood Oct. 7, 1924 SkillmanFeb. 9, 1937 Watson Apr. 15, 1941 8 Kuhne Sept. 29, 1942 Brown July 20,1943 Heim Dec. 14, 1954 Herbanar July 2, 1957 Spriggs Dec. 3, 1957Herbenar Mar. 18, 1958 FOREIGN PATENTS Great Britain 1927

1. A RESILIENT PIVOTAL BUSHING ASSEMBLY COMPRISING A PAIR OF BUSHINGMEMBERS ARRANGED ONE CONCENTRIC ABOUT THE OTHER, SAID MEMBERS HAVINGOPPOSED BEARING SURFACES EXTENDING AXIALLY OF THE BUSHING ASSEMBLY UPONWHICH SURFACES SAID BUSHING MEMBERS ARE ROTATABLE RELATIVE TO EACH OTHERIN SAID CONCENTRIC ARRANGEMENT, THE BEARING SURFACES OF EACH OF SAIDMEMBERS BEING IN THE FORM OF A RIB DISPOSED HELICALLY ALONG THERESPECTIVE BUSHING MEMBERS, THE HELICAL RIB OF ONE BUSHING MEMBERINTERMESHING WITH THE HELICAL RIB OF THE OTHER BUSHING MEMBER, AT LEASTONE OF SAID RIBS BEING OF RESILIENT RUBBER, AN ANNULAR RESILIENT RUBBERBODY ON ONE END OF ONE BUSHING MEMBER, A BEARING SURFACE FORMED ON SAIDRUBBER BODY AND DISPOSED GENERALLY TRANSVERSELY OF THE BUSHING ASSEMBLYAND ROTATABLY ENGAGED WITH A MATING TRANSVERSE BEARING SURFACE ON SAIDOTHER BUSHING MEMBER, SAID TRANSVERSE BEARING SURFACES BEING PRESSEDAGAINST EACH OTHER IN ROTARY ENGAGEMENT IN RESPONSE TO AXIAL THRUSTLOADS ON THE BUSHING ASSEMBLY, AND SEALING MEANS AT THE END OF SAIDBUSHING ASSEMBLY OPPOSITE SAID TRANSVERSE BEARING SURFACES, SAID SEALINGMEANS INCLUDING AN ANNULAR RIB ON ONE BUSHING MEMBER AND AN ANNULARCHANNEL IN THE OTHER BUSHING MEMBER WIDER THAN SAID RIB INTO WHICH SAIDRIB PROJECTS WHEREBY SAID BUSHING MEMBERS ARE ADAPTED FOR LIMITEDUNRESTRICTED RELATIVE ROTATION IN REVERSE DIRECTIONS FROM A NEUTRALCENTRAL ASSEMBLED POSITION OF SAID INTERMESHED HELICAL RIBS.